The present invention relates to a microsurgical cutting instrument to be used in surgical treatment of glaucoma by means of a novel operational procedure, which significantly may be called "selective trabeculectomy".
Glaucoma is an ailment resulting in increased inner pressure in the eyeball. Within the eye, aqueous humor is produced at a fairly constant rate. This liquid is drained out through filterlike tissue (trabecular meshwork) in the area between iris and cornea into a collector canal running circularly along the transition between cornea and sclera (Canal of Schlemm), and from this canal through 20-30 drainage outlets in the eye wall into blood vessels (water veins).
The cause of glaucoma is believed to be a type of "clogging" of the trabecular meshwork, so that the outflow resistance increases. Then, also the pressure increases to allow the same volume of liquid to be drained out per time unit. All treatment aims at reducing the eye pressure. Such treatment is primarily medical, but when this is intolerable and/or insufficient, surgical treatment is used.
The surgical treatment may be subdivided according to three principles, namely:
1. Operations aiming at reduced production of aqueous humour.
2. Fistulizing procedures, i.e., surgical provision of artificial slits in the eye walls through which the liquid may seep out of the eye.
3. Operations on the trabecular meshwork. Existing procedures of this kind are of two types, i.e.:
(a) Approach through the anterior chamber of the eye by means of goniotomy or cautery of the trabecular meshwork with laser beams.
(b) Approach through the Canal of Schlemm. Such approach consists in opening this canal through a radial incision in the eye wall above the canal and insertion of a blunt probe or probe means with a cutting edge (trabeculotome). This instrument is then manipulated in such a way that it tears open or cuts through the trabecular meshwork into the anterior chamber of the eye. With such procedure a narrow slitlike opening is formed through the trabecular meshwork. Such slits exhibit, however, a considerable tendency to close.